[多选题]24. When configuring the CA CRL revocation-retrieval policy, which methods are available? (Choose all that apply.)当配置CA的CRL吊销一检索策略时，哪一种方法是可用的?(选择所有满足提条 件的答案)
A.FTP
B.HTTPS
C.HTTP
D.TFTP
E.LDAP
F.SCEP